I've been thinking of doing the omgwtf cut, but as it being my first portable I don't know if I should or not.
If you can follow instructions carefully and have an OK soldering iron, I think anyone can do an OMGWTF. Pretty much every time someone fails a trim is because they are using a $10 iron, or they just aren't following the guide like they should.
I plan on using
https://m.ebay.com/itm/PTH08080WAH-...put-Out-Adj-Mini-Pwr/322563128439?_mwBanner=1 for the regulators. The forum for the basics of regulators recommended using 4x PTH08080 regulators
Those regs are the right kind. These are a bether deal though if you want to save a few bucks. The link you gave actually only comes with one PTH, it's pretty misleading.
Battery I haven't chosen yet I'm looking for a 7.4v battery (I'm not sure if a higher mAh or a lower mAh is better). Also if I could buy any overcharge protection circuit or one already with the battery, if you have an recommendations that would be nice.
You can buy premade battery packs like portable phone chargers, which already have protection circuitry and stuff built in, or you can design your own circuit. Just be wary of both packs and cells that lie about their capacity.
We've got a thread with information about all things batteries, so be sure to check it out.
For the screen im just going to use a 5inch screen that uses HDMI and get an adapter for the Wii and leave it inside the the portable.
HDMI inside a WiiP can work and does produce nice video, provided you don't get a cheapo one. I believe the Sewell brand is one of the nicer ones, but someone would have to back me on that. We don't generally reccomend using HDMI inside of Wii portable, because it requires hard wiring in that bulky and power-hungry convertor. Luckily though, there areally a couple of options opening up for 5 inch screens with higher quality video coming soon. Paging
@Stitches to remind him to finish up that thread
Essentially, I'd wait a little while before making any sort of purchase on a screen.
Good luck with this! Don't worry about having lots of questions, everyone has them.